1. Field of the Invention
This invention relates to data authentication and, more particularly, to techniques for detecting alteration of audio data, image data, or both.
2. Description of Background
Audio and image data may be stored to create records of court proceedings, to document conversations held during business meetings, and to archive information that is broadcast via television or radio. In many situations, data tampering leads to risks in safety and security. For example, many court cases rely upon audio evidence to convict or exonerate a suspect, thereby creating a perilous situation if a guilty party is set free as a result of data that is deliberately altered. Likewise, radio and television stations often broadcast archived data. If erroneous information is broadcast in relation to an impending terrorist attack or natural disaster, panic may ensue. In the case of image data, identifying the source of an image or photograph is difficult if the image has been modified or enhanced. For example, an image taken from a computer and brightened using a photo editing program may appear different from the original when, in fact, it is a copy of the original photo. This technique is often utilized by distributors of pornography who avoid being linked to their merchandise by modifying images before the images are distributed.
Existing methods for detecting alterations to audio and image data involve analyzing a unique digital fingerprint of the actual data. Each audio sample or visual image is encoded with a known “fingerprint” or digital signature that will change if the original data is modified. However, if the data in question is stored in analog form, it is not possible to use the digital signature to detect data alteration or tampering. When digital data is converted into analog data, all digital signatures are lost along with the security features provided by these signatures. Moreover, in many cases, digital signatures can be manually modified with existing technology, such that two different sets of data are made to appear identical based upon their digital signatures, thereby reducing the effectiveness of the digital signature approach for detecting data alterations. In view of the foregoing considerations, what is needed is an improved method for detecting alterations to audio or image data.